It is known to produce ophthalmic lenses, in particular contact lenses such as soft contact lenses, in an automated manufacturing process using reusable molds. In mass production of contact lenses, specifically disposable lenses which are worn only once and are then disposed of, a high number of contact lenses must be manufactured in a relatively short period of time. In an embodiment of such process for the mass production of soft contact lenses, a lens forming material, for example a polymer or prepolymer solution, is introduced into a female mold half, the mold is closed by the respective male mold half, and then the lens forming material is polymerized and/or cross-linked with the aid of ultraviolet (UV) light to form the contact lens. The mold is subsequently opened and the lens is removed from the male or female mold half of the opened mold. Suitable polymers formed by photochemical polymerization of suitable prepolymers include polymers based on polyvinyl alcohols (PVA) or silicone hydrogels (SiHy).
After removal of the lens from the male or female mold half, the male and female mold halves are cleaned so as to remove any lens forming material or other residues that may have deposited on the molding surface. During cleaning of the mold the molding surface is exposed to a jet of a cleaning liquid, which may comprise deionized water and/or organic solvents, and is subsequently dried. However, despite this cleaning process the deposits may not absolutely completely be removed from the molding surface. And although such minimal amounts of deposits may accumulate on the molding surface over a considerable number of production cycles they are so small that the contact lenses produced are well within the specifications as regards their optical and geometrical properties, so that these lenses are not detected as being defective during optical inspection. The residues on the molding surface may be so small that over a considerable number of production cycles they may not even be visible on the molding surfaces. However, as the number of production cycles continues to grow the deposits on the molding surface may accumulate more and more until they may reach a level where the contact lenses are detected as not being within the specifications during the inspection process. From that time, continuing production of contact lenses using this mold would lead to contact lenses which are rejected due to the lenses being outside the specifications.
Therefore, in order to obtain fault-free contact lenses which are well within the specifications the deposits must be reliably removed from the molding surface on a regular basis, and in particular the deposits have to be removed before they have accumulated to an amount where the contact lenses produced from the mold having the accumulated deposits on its molding surface are detected as being defective. And while methods for abrasively cleaning these deposits from the reusable molds are available, such abrasive cleaning may result in the molding surface of the mold getting damaged, and this molding surface is a surface that must have optical quality and must be able to stand a high number of production cycles. Since the reusable molds are very expensive, abrasion of the molding surface must be prevented while at the same time the molding surface must be reliably cleaned.